The Scottish 1921 census lists a Benjamin Solomon aged 47 in Gorbals - maybe worth buying some credits?
https://www.scotlandspeople.gov.uk/record-results/112208774163cc795faf5ce?check_logged_in=1
Thanks. Your link is broken but I need to sign up to FindMyPast for another 1921 census so will look into this at the same time. This man is certainly the same man as in The Scotsman that you mentioned previously as Gorbals seems to be a two minute walk from Thistle Street.
I have since discovered this attachment. Possibly his naturalisation record in the SA archives. Unfortunately it seems that one needs to either visit the archives in person, or hire a researcher to gain access to the certificate.
I'm unsure whether both of these naturalisation records are him, or if only one of them is him.
This is what I have so far:
Applied for naturalisation 1904-1906 from SA. -- unsure if him
Immigration record from 1910. Ship from Kourland, Russia to SA. States "years of residence/service under the crown: 6" on the record -- unsure if him
SA Marriage in 1911. Wife also from Kourland, died in SA, 1912. -- unsure if him
Served in British Army WW1. -- unsure if him
Naturalisation record at British National Archives 1919. -- unsure if him
Marriage banns to my GGM in SA, 1928. He's listed as a widower -- confirmed
My Grandmother and siblings baptisms with his name again in SA -- confirmed
Just need to connect the dots... Hopefully the National Archives nat. certificates may give a clue.